In the past, the use of the inter-layer inhibiting effect was known as a means of improving color reproduction in color photographic photosensitive materials. Taking color negative sensitive materials as an example, it is possible to suppress the formation of color in the red sensitive layer on white light exposure to a greater extent than in the case of red light exposure by imposing a development inhibiting effect from the green sensitive layer to the red sensitive layer. The color negative paper system is such that on exposure to white light, the gradation is balanced so as to reproduce gray on the color print and so the aforementioned interlayer effect gives a higher density cyan color formation on red light exposure than with gray exposure. As a result, it is possible to suppress cyan color formation on the print and reproduce a red color which has a higher degree of saturation. Similarly, a development inhibiting effect from the red sensitive layer to the green sensitive layer gives green reproduction with a high degree of saturation.
The method in which use is made of iodine ions which are released from the silver halide emulsion during development is known for increasing the interlayer effect. That is to say, in this method the silver iodide content of the donor layer of the interlayer effect is increased and the silver iodide content of the acceptor layer is reduced. Another method of increasing the inter-layer effect involves adding couplers which release development inhibitors on reaction with the oxidation products of the developing agent in a paraphenylenediamine based color developer to the donor layer of the inter-layer effect, as disclosed in JP-A-50-2537. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".) Another method of increasing the interlayer effect is known as auto-masking. In this method, a colored coupler is added for a colorless coupler to mask the unwanted absorptions of the colored dye of the colorless coupler. The methods depending on colored couplers increase the amounts added and provide masking beyond the masking of the unwanted absorption of the colorless couplers, and they can provide an effect which is the same as the interlayer effect.
If the saturation of the red, green and blue primary colors is increased using these methods, there is a disadvantage in that the green hue from yellow and cyan is not reproduced faithfully, and the technique disclosed in JP-A-61-34541 has been proposed to counter this disadvantage. This technique provides bright and faithful color reproduction by means of silver halide color photographic photosensitive materials comprising a support having thereon at least one blue sensitive silver halide emulsion layer which contains a color coupler which forms a yellow color, at least one green sensitive silver halide emulsion layer which contains a color coupler which forms a magenta color and at least one red sensitive emulsion layer which contains a color coupler which forms a cyan color, wherein the sensitivity wavelength at the center of gravity of the spectral sensitivity distribution of the green sensitive layer (.lambda..sub.G) is 520 nm.ltoreq..lambda..sub.G .ltoreq.580 nm, and the center of gravity wavelength of the distribution of the size of the interlayer effect which is received by at least one red sensitive silver halide emulsion layer which forms a cyan color from the other layers in the region from 500 nm to 600 nm (.lambda..sub.-R) is 500 nm.ltoreq..lambda..sub.-R .ltoreq.560 nm, and .lambda..sub.G -.lambda..sub.-R .gtoreq.5 nm.
A interlayer effect on the green sensitive layer also arises from the layer which imparts the interlayer effect on a red sensitive layer. In order to prevent the imposition of undesirable effects on color reproduction, it is desirable that the layer which imparts the interlayer effect on a red sensitive layer forms a magenta color.
It is known that graininess of human skin is liable to arise on color prints on taking photographs using sensitive materials which have been obtained in this way. On analyzing the cause of this effect, it is found to be due to the fact that the graininess of the magenta color formation by the silver halide emulsion layer which imparts a interlayer effect to the red sensitive layer is poor in comparison with the graininess of the other color forming layers.
The reason why the graininess of the layer which imparts the interlayer effect to the red sensitive layer is worse than the graininess of the other silver halide emulsion layers is because the sensitizing dyes (center of gravity wavelength: 500 nm&lt;.lambda..sub.-R &lt;560 nm) used conventionally in the silver halide emulsion layers for providing the interlayer effect have had a low color sensitizing efficiency because of their weak absorption, so that the speed/graininess ratio becomes poor.
Hence, a demand has arisen for sensitizing dyes which provide a strong absorption (spectral sensitivity) in the center of gravity wavelength range from 500 to 560 nm (and preferably in the range from 520 to 540 nm) from the viewpoint of color reproduction.